Tri-fold frame constructions are well known in the prior art, and actually have been the standard construction in the industry for years. Although a variety of different mechanisms are employed to permit these tri-fold constructions to be oriented into different positions, the operating mechanisms often are difficult to use, and in many cases can actually damage the floor or other supporting surface when being opened from a seating piece orientation to a bed frame orientation.
One of the major disadvantages of prior art tri-fold constructions is the difficulty of converting the frame from a bed to a couch. First, the futon (which functions as the mattress of the bed) must be folded in half to expose the back or rear portion of the frame. Thereafter, the exposed frame section must be raised and locked, and then the entire frame, with the futon on it, must be slid back to the original position, usually against a wall. This is not an easy task, in view of the fact that the combined frame and futon weighs on the order of 100-140 pounds. Thus, what is intended to otherwise be a versatile piece of furniture, in actuality is difficult to use, and therefore unappealing. In fact, these prior art constructions may be impossible to operate by many individuals, such as individuals of small stature, individuals having little strength, or individuals that are elderly and/or handicapped.
Another disadvantage of some prior art tri-fold constructions becomes apparent when converting the frame from a "couch" or "chair" position, to a bed configuration. In order to accomplish this conversion the seat section generally is pulled out first, to thereby cause all three sections to pivot relative to each other. However, at some point the combined weight of the frame and futon overcomes the frictional resistance to sliding movement of the back section, resulting in both the middle and back sections collapsing to the floor. This often provides a very loud and disturbing noise, particularly in situations where the floor is not carpeted, which is often the case in studio apartments, dormitories and temporary housing in which the use of futon frames is becoming quite popular.
In applicant's earlier invention, as described and claimed in U.S. Pat. No. 5,170,519, the above-described problems associated with tri-fold frame constructions were solved, and the mechanisms employed in the '519 construction for solving such problems also are employed in the invention described herein. The subject matter of the '519 patent is fully incorporated herein by reference.
In a tri-fold construction constituting a modification of that disclosed in the '519 patent a number of pairs of discrete legs are provided to support the frame on the floor or other supporting surface. One pair of such legs is located at the junction of the rear and intermediate sections of the frame, and each leg of this pair is required to be movable relative to the frame-support member to which it is secured in order to permit these latter frame sections to be properly moved between the "couch" and "bed" orientations of the frame construction. Moreover, in the bed orientation the movable legs must be positioned in a proper orientation to support the frame member on the ground or other supporting surface, and also need to be "locked" in that proper orientation to preclude the legs from wobbling or collapsing either in use or when the opened frame construction (i.e., the bed orientation) is moved along its supporting surface.
In one prior art arrangement, flexible straps are connected to slats of intermediate and rear frame members of the tri-fold unit, and also to the movable legs located at the junction of such frame members. The lengths of the straps are such that the straps are intended to be maintained in a taught condition when the frame construction is in a fully opened orientation (i.e., in the bed orientation) to preclude undesired pivotal movement of the legs.
The above-described prior art strap arrangement has at least two major drawbacks. First, the straps need to be physically secured to both the intermediate and rear frame members and to the legs at the point of manufacture, thereby increasing the complexity (and cost) of the manufacturing operation. Second, in the event that one or more of the interconnecting straps either breaks in use or becomes separated from the pivotal leg, the frame could collapse and thereby become damaged. Moreover, home repair of the broken or separated strap can be deficult for the average person.
Thus, the need exists for a simplified and reliable mechanism or system for overcoming the above-described deficiencies of the prior art construction employing straps. The present invention relates to just such a system.